Heat transfer control



1966 R. s. KOMAROW HEAT TRANSFER CONTROL Filed Sept. 24, 1965 INVENTOR.Poss/QT 5, KOMHROW HTTORNEYS United States Patent 3,229,755 HEATTRANSFER CONTROL Robert S. Komarow, Yonkers, N.Y., assignor to UnitedAircraft Corporation, East Hartford, Conn.-, a corporation of DelawareFiled Sept. 24, 1963, Ser. No. 311,142 6 Claims. (Cl. 165-32) Myinvention relates to a heat transfer control and more particularly to adevice for controlling the temperature of a body Without the use of anexternal source of power.

Many devices are known in the prior art for controlling or regulatingthe temperature of a body. These devices employ some active means whichadds heat by a separately powered heating element or the like or whichremoves heat by means of a separately powered refrigerating system. Allof the devices of this type require a source of power which is externalto the body being controlled.

There are many instances in which a body must be maintained at a giventemperature but wherein power available is limited. There are otherapplications in which the control of temperature must be made withoutthe use of convection as a mode of heat transfer owing to the absence ofatmosphere. Examples of instances where power is not available or islimited and in which convection cannot normally be used as a mode ofproducing heat transfer are in satellites and missiles and the like.

I have invented a heat transfer control which permits regulation of thetemperature of a body without requiring external power. My device doesnot require heat transfer by convection. My control is extremely rugged.It is simple in construction and operation for the result achievedthereby.

One object of my invention is to provide a heat transfer control whichdoes not require a source of power.

Another object of my invention is to provide a heat transfer controlwhich operates by conduction.

A further object of my invention is to provide a heat transfer controlwhich is extremely rugged.

Still another object of my invention is to provide a heat transfercontrol which is simple in construction and operation for the resultachieved thereby.

Other and further objects of my invention will appear from the followingdescription.

In general my invention contemplates the provision of a heat transfercontrol for regulating the temperature of a body in which I couple thebody to a heat sink through a variable heat conductor. Means responsiveto the temperature of the controlled body varies the heat conductance ofthe variable conductor to regulate the rate at which heat leaves thecontrolled body.

In the accompanying drawing which forms part of the instantspecification and which is to be read in conjunction therewith:

The figure is a diagrammatic sectional view of one form of my heattransfer control.

Referring now to the figure, my heat transfer control is adapted for usewith a body 10, the temperature of which is to be regulated orcontrolled by the transfer of heat from the body to a heat sink 12. Mytransfer control comprises a housing 14 formed of conductive metal suchas silver or copper or the like embedded within the controlled body 10.A stationary heat conductor 16 formed of similar metal in engagementwith the body 10 connects the housing 14 to an intermediate housingsection 18.

A heat conductor 20, similar to conductor 16, in intimate engagementwith the heat sink 12 joins the intermediate housing portion 18 to ahousing 22 embedded in the heat sink 12.

My control comprises a variable heat conductor element formed of heatconductive material indicated generally by the reference character 24,having a relatively large diameter portion 26 and a portion 28 ofreduced diameter. It will readily be apparent that the portion 23 of theconductor 24 provides a relatively high resistance to the transfer ofheat therealong as compared with the portion 26. I provide theconductors 16 and 20 with respective bores 30 and 32 which slidablyreceive the portions 26 and 28 of the conductor 24. An annular recess 34in conductor 16 receives a conductive packing 36 adapted to providereduced frictional resistance and low resistance to heat transfer fromthe conductor 16 to the conductor portion 26. The packing 36 may, forexample, be fine silver or copper wire in the form of wire wool orsilver or copper amalgam packed into the recess 34. Advantageously athin film of polytetrafluoroethylene may be applied to the conductingsurfaces of conductor 24 to reduce friction. Further, if amalgam isemployed for packing the synthetic resin will prevent the mercury fromreacting with the sliding surfaces of conductor 24. I form the conductor20 with an annular recess 38 for receiving a conductive packing 40similar to the packing 36, which ensures reduced friction and readytransfer of heat from the conductor 20 to the portion 28 of theconductor 24.

From the structure just described, it will readily be apparent that thevariable conductor 24 is supported for sliding movement with relation tothe stationary conductors 16 and 22 carried respectively by the body 10,the temperature of which is to be controlled and .by the heat sink 12 towhich heat is to be conducted.

The housing 14 is formed with a reservoir 42 at its lower end. A conduit44 connects the reservoir 42 to the interior of a bellows 46. A screw 48mounted on the bellows 46 by any suitable means such as by welding,brazing or the like is threaded into the portion 26 of the variableconductor 24.

In the particular embodiment of my invention illustrated in the drawing,I fill the reservoir 42 with an expansible fluid such, for example, asmercury. A spring 50 disposed within the housing 22 acts on a plate 52screwed on portion 28. The zero position of the device can be adjustedby turning plate 52 to position it on the portion 28 to regulate theforce exerted on conductor :24 by the spring 50. A set screw 54 holdsplate 52 in its adjusted position.

In operation of my heat transfer control, heat flows in the direction ofthe arrows along paths indicated by broken lines in the figure from thecontrolled body 10, through the conductor 16, through the packing 36,through the relatively low resistance portion 26 of conductor 24,through the relatively high resistance portion 28 of conductor 24,through packing 40 and through the fixed conductor 20 to the heat sink12.

The rate of heat transfer by conduction between two points along alength of material is given by the relationship 1 2) A q s where s isthe distance between the points t t is the temperature diiferencebetween the points A is the cross sectional area k is the conductivityof the material With k expressed in cal./sec./ C./cm., q will be incaL/sec.

From the relationship given above it is clear that for a given length ofmaterial the rate of heat transfer along a rod of greater diameter willbe higher than the rate along a rod of smaller diameter.

It will readily be apparent that the rate of heat transfer along thispath from the body to the body 12 is determined by the relative lengthsof the portions 26 and 28 disposed between the two fixed conductors 16and 20. That is, if most of the space between the fixed conductors isoccupied by the large diameter portion 26, the rate of heat transferwill be relatively great as compared with the rate when most of thespace between the fixed conductors is occupied by the smaller diameterportion 28.

' Expressed another way, the portion of the conductor 24 between thefixed conductors 16 and 20 comprises a variable heat conductor, thevalue of which is determined by the position of the variable conductor24.

The mercury within the reservoir 52 acts so as to position the conductor24 to maintain the temperature of the body 10 at thedesired temperature.For example, assuming that the temperature of the body 10 rises to abovethe desired temperature, the mercury 52 within chamber 42 expands toexpand the bellows 46 to move the conductor 24 upwardly as viewed in thefigure. As the conductor 24 moves upwardly, a greater proportion of thespace between the fixed conductors 16 and 20 is occupied by the portion26 and the rate of flow of heat from the body 10 to the sink 12 iscorrespondingly increased. The effect of this increased rate of heattransfer is to reduce the temperature of the body 10.

Conversely, if the temperature of the body 10' drops below the desiredtemperature, mercury 52 contracts and spring 50 compresses the bellows46 by moving the conductor 24 downwardly as viewed in the drawing. Thismovement of the conductor 24 downwardly results in portion 28 occupyinga relatively greater percentage of the space between the fixedconductors 16 and 20 to produce a corresponding reduction in the rate oftransfer of heat from body 10 to heat sink 12 to permit a correspondingincrease in temperature of the body 10. The over-all result of theaction of the mercury on the conductor 24 is to maintain the temperatureof body 10 substantially constant.

While I have shown a form of my heat transfer control :wherein I employthe mercury reservoir 42 as the heat sensitive element, it will readilybe apparent that I can as well use any other means for actuating thevariable conductor such, for example, as an enclosed gas or a bimetallicstrip or a solenoid or any other suitable control. It will further beclear that the control can be achieved by sensing the temperature of theheat sink rather than of the controlled object, if desired.

It will be seen that I have accomplished the objects of my invention. Ihave provided a heat transfer control which does not require a source ofpower. My heat transfer control does not rely on convection to achieveits purpose. It is extremely rugged so that it can withstand shocksincident to its use. It is simple and compact for the result achievedthereby.

It will be understood that certain features and subcombinations are ofutility and may be employed without reference to other features andsubcombinations. This is contemplated by and is within the scope of myclaims.

Having thus described my invention, what I claim is:

1. A control for governing the heat transfer between two thermallyconductivebodies separated by a relatively insulating space including incombination an elongated element of thermally conductive material, saidelement having a first length with a certain cross-sectional areaproviding a given heat transfer along said length and having a secondlength with a cross-sectional area less than said certaincross-sectional area providing a heat transfer along said second lengthless than said given heat transfer, thermally conductive means mountingthe respective lengths for movement relative to said bodies and in heattransfer relationship therewith with the junction between said lengthsin the space between the bodies and means responsive to the temperatureof one of the bodies for positioning said junction in said space toregulate the heat transfer between the bodies through the element.

2. A device as in claim 1 in which said mounting means each comprises aconductive block and conductive packing between said block and theassociated length to reduce the frictional resistance of said lengths tosaid sliding movement.

3. A device as in claim 1 in which said'temperature responsive meanscomprises an exipansible bellows connected between one of said lengthsand the associated body and a thermally expansible fluid in said bellowsand a spring disposed between the other of said lengths and itsassociated body and acting against said bellows.

4. A device for regulating the rate of heat transfer between twothermally conductive bodies separated by a relatively insulating spaceincluding in combination an elongated element having a first relativelyhighly thermally conductive length and a second relatively lessconductive length, a heat conductive junction between the two lengths,thermally conductive means slidably mounting.

said first length for movement relative to one of said bodies and inheat transfer relationship therewith, thermally conductive meansmounting the second length for sliding movement relative to the other ofsaid bodies and in heat conductive relationship therewith whereby saidjunction is positionable in said space and means responsive to thetemperature of one of said bodies for moving said element in thedirection of its length to determine the position of said junction insaid space to regulate the heat transfer between said bodies throughsaid element.

5. A device for regulating the heat transfer between two thermallyconductive bodies separated by a relatively insulating space includingin combination an elongated element having a first relatively highlythermally conductive length and a second relatively less conductivelength, said lengths connected by a thermally conductive junction,thermally conductive means coupling said first length to one of saidbodies in heat transfer relationship therewith, thermally conductivemeans coupling the second length to the other of said bodies in heattransfer relationship therewith whereby said junction is in said spaceand means for moving said element in the direction of its length.

6. A device for regulating the heat transfer between two thermallyconductive bodies separated by a relatively insulating space includingin combination an elongated element formed of the same conductivematerial throughout, said element having a certain cross-sectional areaover a first length thereof providing a given heat transfer along saidlength and having a cross-sectional area less than said certain areaover a second length thereof providing a heat transfer less than saidgiven heat transfer along said second length, means thermallyconductively connecting said element to said bodies with the junctionbetween said lengths in said space and means for moving said element inthe direction of its length.

(References on following page) References Cited by the Examiner UNITEDSTATES PATENTS Beler 23699 Mott 62-50 X Widstrom 23 6-1 Davidson et a1.23699 Ferranti 126211 Winfield 62-159 Smelling 236--1 6 OTHER REFERENCESHandbook of Chemistry and Physics, 38th ed., Chemical Rubber PublishingCo., Cleveland, Ohio, 1956, pp. 1460, 1461.

ROBERT A. OIJEARY, Primary Examiner.

ALDEN D. STEWART, CHARLES SUKALO,

Examiners.

1. A CONTROL FOR GOVERNING THE HEAT TRANSFER BETWEEN TWO THERMALLYCONDUCTIVE BODIES SEPARATED BY A RELATIVELY INSULATING SPACE INCLUDINGIN COMBINATION AN ELONGATED ELEMENT OF THERMALLY CONDUCTIVE MATERIAL,SAID ELEMENT HAVING A FIRST LENGTH WITH A CERTAIN CROSS-SECTIONAL AREAPROVIDING A GIVEN HEAT TRANSFER ALONG SAID LENGTH AND HAVING A SECONDLENGTH WITH A CORSS-SECTIONAL AREA LESS THAN SAID CERTAINCROSS-SECTIONAL AREA PROVIDING A HEAT TRANSFER ALONG SAID SECOND LENGTHLESS THAN SAID GIVEN HEAT TRANSFER, THERMALLY CONDUCTIVE MEANS MOUNTINGTHE RESPECTIVE LENGTHS FOR MOVEMENT RELATIVE TO SAID BODIES AND IN HEATTRANSFER RELATIONSHIP THEREWITH THE JUNCTION BETWEEN SAID LENGTHS IN THESPACE BETWEEN THE BODIES AND MEANS RESPONSIVE TO THE TEMPERATURE OF ONEOF THE BODIES FOR